Solid stick corrosion inhibitors and a process for preventing corrosion of oil and gas well equipment



Patented June 3, 1952 T E S SOLID STICK CORROSION INHIBITORS AND A PROCESS FOR PREVENTING CORRO- SION OF OIL AND GAS WELL EQUIPMENT N Drawing. Application July 9, 1951, Serial No. 235,906

1 Claim. (or. 252-855) This invention relates to improved, products for the inhibition of corrosion of oil and gas well equipment, and more particularly to a corrosion inhibitor in the form of a solid, weighted stick which may be introduced into the well and allowed to fall to the bottom where it disintegrates, becomes dissolved or dispersed in the fluid and is brought by it into contact with the metal surfaces of the well.

In our prior application Serial No. 154,824, filed April 8, 1950, we have described the problems involved in providing a suitable weighted stick inhibitor and have there described a special type of three-component vehicle which we have found may be used successfully with weighting material and inhibitor to produce a stick of high specific gravity adapted for corrosion inhibition in certain types of wells where introduction of a corrosion inhibitor in liquid form or in conventional low density (e. g., specific gravity about 1.0) stick form is impractical. We have also there described the conditions under which inhibitors in weighted stick form are advantageously used and the characteristics which they must have for commercial utility.

We have now found that weighted stick inhibitors may be successfully prepared using imidazoline inhibitors of the type described in said application Serial No. 154,824 and in Patent Re. 23,227, granted May 9, 1950, conventional weighting materials such as lead oxide, powdered lead, barium sulfate, barium oxide, or other dense, comminuted materials with a vehicle consisting of an oxidized mineral Wax having a saponification value between about 50 and about 180, and a hardness, as determined by needle penetration (100 gr. weight, 5 secs.) of less than 50 mm. Advantageously, the oxidized wax has a saponification value between 80 and 170 and needle penetration value between 5 and 20. Products with saponification values below 50 are inadequately compatible with the imidazoline constituent to produce sticks of satisfactory physical properties. Oxidized waxes with saponification values above about 180 are too soft or tacky to give a product of satisfactory physical properties.

While eminentl satisfactory products can be formed from the three components outlined above, in proper proportions, which are from 20 to 65 parts of the imidazoline inhibitor to 80 to 35 parts of the oxidized wax with an amount of weighting material to give the desired density, for example, 125 parts of litharge to give a product of density of about 2.0 or 60 parts of litharge to give a density of about 1.5 (about theminimum feasible) addition of a polymeric material which adds toughness to the compositions, as, for example, polyethylene, cellulose esters or ethers, or the like, in minor proportions, for example, from 10 to 20% of such a material, based upon the total of the constituents of the stick excluding the weighting material, is in some cases advantageous.

The underlying discovery upon which the invention is based is that the properly selected oxidized mineral waxes have physical properties and compatibility with, or solvent power for, the imidazoline inhibitors such that a weighted stick of correct physical properties is obtainable without the use of additional vehicle components.

These oxidized mineral waxes are known materials. They are prepared, usually, by blowing air through molten mineral wax at a temperature of about 220 to 330 F., usually with the use of a catalyst such as-potassium permanganate, cobalt salts, manganese or iron soaps or other oxidation catalyst for a, period of time sufiicient to raise the saponification value to the required level. Any of the available mineral waxes may be used to produce these oxidized products, including paraffin Wax, microcrystalline wax produced from lubricating oil fractions, and high melting point microcrystalline waxes obtained from crude oil or tank bottoms. The waxes which are oxidized need not be completely oil free. Thus, the socalled petrolatums may be used providing the oil content is not so high as to give an oxidized product having a needle penetration gr. weight, 5 secs.) of more than 50 mm. Furthermore, the oxidized wax may be one of relatively high saponification number which is cut back with unoxidized mineral wax, providing the amount of unoxidized wax which is included does not reduce the saponification value of the mixed wax below 50 and advantageously not below '70.

Typical useful oxidized mineral waxes are one having a melting point of 185 F., needle penetration (100/5) of 6 mm., color NPA of 6, saponification value 55 and acid value 20 obtained by conventional blowing of a microcrystalline wax having a melting point of 195 F. obtained from tank bottoms. Another useful product produced from the same microcrystalline wax has a melting point of 182 F., needle penetration (100/5). of 8 mm., color NPA of 8, saponification value 85, and acid value 35. Another useful product produced by blowing an oily parafiin of F. melting point, has a melting point of 144 F., a needle penetration (100/5) of 35 mm., saponification value and acid value 54.

For convenience, in the examples which follow these three products will be designated Crown 23, Crown 36, and Wax Ester 60, the trade-marks under which they are commercially available, respectively.

The inhibitors which are included in the weighted stick inhibitors of the present invention are known and have been used on a considerable scale for corrosion inhibition, particularly in oil and gas wells. They are described in the said Patent Re. 23,227. They are substituted imidazolines which may be represented by the generic formulae:

in which B is hydrogen, methyl or ethyl, at least three occurrences of B being hydrogen, and in which D represents a divalent, non-amino organic radical containing less than 25 carbon atoms, composed of elements from the group consisting of C, H, O, and N; D represents a divalent organic radical containing less than 25 carbon atoms, composed of elements from the group consisting of C, H, O, and N, and containing at least one amino group; and R. is a member of the class consisting of hydrogen and aliphatic and cycloaliphatic hydrocarbon radicals, with the proviso that at least one occurrence of R contains 8 to 32 carbon atoms.

Such products are obtained by condensation of monocarbo-xy acids and polyamines, which polyamines contain at least one primary amino group and a secondary amino group or another primary amino group separated from the first primary amino group by two carbon atoms, in particular such amines as ethylene diamine, diethylene triamine, triethylene tetramine, tetraethylene pentamine, pentaethylene hexamine, the high boiling polyamines remaining when the reaction mixture used for the production of tetraethylene pentamine is distilled, polypropylene amines and polybutylene amines, in which the required amino groups described above are present, and the like. Typical useful imidazoline inhibitors are the products obtained by heating 815 parts of commercial stearin with 585 parts of tetraethylene pentamine for three hours at 290 C., the product obtained by heating 815 parts of commercial tall oil with 310 parts of triethylene tetramine for three hours at 280 C. and the product obtained by heating 775 parts of commercial rosin with 400 parts of the polyamino residue resulting from the distillation of tetraethylene pentamine from the reaction mixture in which it is produced for three hours at 280 C. These inhibitors may be used as such or they may be used in the form of salts, as, for example, the salts of monocarboxy detergent-forming acids, such as the salts of higher fatty acids, abietic acid, rosin, naphthenic acids and the like, or in the form of amides obtained by amidification of the imidazolines with monocarboxy acids of the same type.

The following examples illustrate typical products of the invention.

Example I parts of the imidazoline obtained from commercial rosin and the high boiling polyamine as described above are melted together with 50 parts of Wax Ester oxidized wax at 200 C. When a homogeneous mass is obtained the mixture is cooled to 150 C. and 125 parts of litharge are added, and stirred in until it is evenly dispersed.

The mixture is then cast into cylinders 1 /2" in diameter and 18" long to produce a stick with a density of about 2.0.

Example II 25 parts of the same imidazoline from rosin, 25 parts of the imidazoline from stearic acid and tetraethylene pentamine described above and 50 parts of Wax Ester 60 oxidized wax are melted together as in Example I and after cooling to 150 C., parts of finely divided barium sulfate are stirred in until evenly dispersed. The mixture is then cast as in Example I to produce a stick with a density of about 1.5.

Example III- 50 parts of the imidazoline from stearic acid and tetraethylene pentamine as described above are melted together with 50 parts of Crown 36 oxidized wax, and then 60 parts of litharge are added at 150 C. after which the product is handled as in Example I to give a stick with a density of about 1.5.

Example IV 20 parts of the imidazoline from rosin described above, 40 parts of Wax Ester 60 oxidized wax and 40 parts of Crown 36 oxidized wax are melted together and 130 parts of finely divided lead are stirred in after which the product is handled as g in Example I to give a stick of density of about 2.2.

Example VI 50 parts of the imidazoline from rosin described above and 50 parts of Crown 23 oxidized wax are melted together and to them are added parts of litharge, after which the product is handled as in Example I to give a stick with a density of about 2.0.

Example VII 50 parts of the imidazoline from tall oil described above, 35 parts of Crown 36 oxidized wax and 15 parts of Ethocel (ethyl cellulose) are melted together as in Example I and 129 parts of finely divided litharge added as in Example I. The stick finally obtained has a density of about 2.0.

Example VIII 65 parts of the imidazoline from tall oil described above and 35 parts of Wax Ester 60 oxidized wax are melted together and to the mixture is added 125 parts of finely divided litharge as in Example I. The resulting stick has a density of about 2.0.

Ewample IX Example X C 50 parts of the abietate of the imidazoline from rosin described above and 50 parts of Crown 36 oxidized wax are melted together as in Example I and then 125 parts of finely divided litharge are added. The stick obtained has a density of about 2.0.

Example XI 50 parts of 2-oleyl imidazoline (from oleic acid and ethylene diamine) and 50 parts of Wax Ester 60 oxidized wax are melted together and to the mixture is added 125 parts of finely divided litharge as in Example I. The resulting stick has a density of about 2.0.

Example XII 50 parts of 2-heptadecyl, l-aminoethyl imidazoline (from stearic acid and diethylene triamine) and 50 parts of Crown 36 oxidized wax are melted together and to the mixture is added 125 parts of finely divided litharge as in Example I. The resulting stick has a density of about 2.0.

Example XIII 50 parts of the oleic acid amide of 2-oleyl imidazoline and 50 parts of Crown 36 oxidized Wax are melted together and to the mixture is added 125 parts of finely divided litharge as in Example I. The stick obtained has a density of about 2.0.

As has been noted above,,in place of the specific imidazolines of the foregoing examples may be used other corrosion inhibiting imidazolines as described in said Re. 23,227 and in our said application Serial No. 154,824.

We claim:

A high-melting solid stick-form corrosion inhibitor for oil and gas well equipment having a specific gravity in excess of 1.5 and having the composition: (a) finely divided weighting material; (b) a substituted imidazoline selected from the class of materials having the formula Ncn2 N-CB RG\ RC\ N- 132 N- B: H I

N'CB2 N-CB2 RC l RC\ \N 13, N- B? R DR in which B is hydrogen, methyl or ethyl, at least three occurrences of B being hydrogen, and in which D represents a divalent, nonamino organic radical containing less than 25 carbon atoms, composed of elements from the group consisting of C, H, O, and N; D represents a divalent organic radical containing less than 25 carbon atoms, composed of elements from the group consisting of C, H, O, and N, and containing at least one amino group; and R is a member of the class consisting of hydrogen and aliphatic and cycloaliphatic hydrocarbon radicals, with the proviso that at least one occur rence of R contains 8 to 32 carbon atoms; and (c) an oxidizedmineral wax having a saponification value between 50 and 180, and a hardness (needle penetration, 100 gm. weight, 5 secs.) of less than 50 mm.; ingredients (b) and (c) being present in relative proportions of 20 to parts of (b) to to 35 parts of (0).

WILLIAM F. GROSS. CHARLES C. ROGERS, JR.

REFERENCES CITED UNITED STATES PATENTS Name Date Blair et al. I May 9, 1950 Number Re. 23,227 

